Industrial production of L-aspartic acid is performed by an enzymatic conversion method using aspartase that uses fumaric acid and ammonia as substrates. L-aspartic acid is highly useful by itself, and can also be converted into various useful chemical derivatives, including L-alanine, 3-aminopropionic acid, acrylic acid, 1,3-diaminopropane, threonine, lysine, methionine, 3-hydroxypropionic acid, cadaverine, 5-aminovaleric acid and the like, by biological methods.
In conventional metabolic engineering methods for improving strains, L-aspartic acid derivatives were produced through a pathway that produces L-aspartic acid from oxaloacetate by use of aspartate aminotransferase. However, in this pathway, the process of producing L-aspartic acid from oxaloacetate involves a reaction that converts glutamic acid to α-ketoglutaric acid, and this reaction was coupled with an NAD(P)H consuming reaction that reproduces L-glutamic acid from α-ketoglutaric acid (Salerno et al., Eur. J. Biochem., 121:511, 1982). Due to such characteristics, the enzymatic reaction that uses aspartate aminotransferase is complicated to use as a major pathway for producing a desired chemical substance, and additionally requires reducing power. Thus, it appears that this enzymatic reaction is less efficient than an aspartase reaction which requires no reducing power and in which ammonia reacts directly with fumaric acid to produce L-aspartic acid.
Accordingly, the present inventors have developed a strain having the ability to produce fumaric acid that is an L-aspartic acid precursor, and have found that, if the expression level of aspartase in the strain is increased to thereby construct a mutant microorganism that uses the aspartase pathway as a major pathway for producing L-aspartic acid, the mutant microorganism can efficiently produce 3-aminopropionic acid (beta alanine), 3-hydroxypropionic acid and 1,3-diaminopropane, which are L-aspartic acid derivatives, thereby completing the present invention.